1. Field of the Invention
This invention relates to a non-volatile semiconductor memory device and more particularly to a non-volatile memory (Electrically Erasable Programmable ROM (Read Only Memory)) such as a NAND type flash memory in which data can be electrically rewritten.
2. Description of the Related Art
Conventionally, in a system containing a processor, an instruction which the processor first receives is output from a non-volatile memory such as a mask ROM or flash ROM. In a non-volatile memory which can output data according to the input state of address pins, the processor is only required to input the address to the non-volatile memory at the power supply turn-ON (startup) time. Particularly, in a NAND type flash memory used as the non-volatile memory, for example, an address area on the memory is specified and a plurality of data items are simultaneously reads out from the specified address area. Then, the plurality of readout data items are serially output in response to clock input of a read enable signal (/RE). In this case, “/” indicates an inverted signal (bar) of the corresponding signal for convenience.
FIG. 13 shows a case wherein the NAND type flash memory with the above configuration is used for startup (booting) of the system, for example. When the power supply of the system is turned ON, for example, a processor (not shown) supplies a startup (readout) control signal to a row address decoder 102 and data register 103. When the readout control signal is supplied, data items in a preset address area (in this example, from page “0”) on a cell array 101 which is previously determined as a set value of the memory are read out to the data register 103. The data items read out to the data register 103 are supplied to an input/output (I/O) buffer 104 and then output to the exterior according to clock input of a read enable signal /RE.
As the memory, a preset memory area corresponding to a plurality of successive addresses starting from the “0” address on the cell array 101 is defined as a data area to store system booting data. The memory is so designed that data items in the data area will be successively output in response to an external clock (read enable signal /RE).
However, the NAND type flash memory is normally used as a file storing memory (file memory). Therefore, it is not always preferable to store system booting data in an area corresponding to the “0” address on the cell array 101. This is because there is a possibility that the data area for the system booting data and a data area (file management data storage area) to store file management data of the file memory will conflict with each other.
As described above, in the prior art, the NAND type flash memory can be used to boot the system, but in this case, there occurs a problem that the data area for the system booting data and a file management data storage area may conflict with each other.